Sand blasting method and apparatus



Dec. 5, 1932- w. A. RQSENBERGER 1,890,164

SAND BLASTING METHOD AND APPARATUS Filed April 21, 1931 2 Sheets-Sheet 1 IWI.

DC 6, 1932- v lw. A. ROSENBERGER 1,890,164

SAND BLASTING METHOD AND APPARATUS Filed' April 21. 1951 2 sheets-sheet '-2 Patented Dec. 6, 1,932

UNITED STATES PATENT OFFICE WILLIAM A. ROSENBEBGER; OF HAGEBSTOWN,

MARYLAND, ASSIGNOB- TO PQANGBORN SAND BLAS'IINGI' METHOD AND APPARATUS Application led April 21,

The invention relates to the sand blasting or cleaning of the inner surfaces of hollow shapes, the method and apparatus being particularly adapted to the cleaning of the inner surfaces of metal tubes or tubular shapes.

The fact is generally accepted and recognized by those skilled in the sand blasting art that, while small tubes of a diameter closely approaching that of the sand blasting nozzle can be cleaned without great diiculty by attaching one end of the tube to the nozzle and passing a continuous stream of air and abrasive through the tube, the amount of compressed air used under these circumstances being governed by the size of the nozzle, the air pressure and the diameter and length of the tube; the sand blasting o relatively large tubes in this way or at least on an economical basis has not been found possible. The ditliculty in cleaning the inside of these larger tubes -bysand blasting seems to be due to the loss of velocity of the air and abrasive within the tube so that the velocity through the tube of such diameters is `insuiicientfor cleaning the inner surface. The experiments which havebeen made in this connection relate to tubes of a diameter thirty to fifty percent larger thanJ that of the nozzle, and to larger diameters 1n connection with which the invention has been developed. While these are the sizes that will be principally discussed in connection with the description and claims, it will be understood that the invention is capable of much more general application.

When the blast is dischargedfrom the nozzle through a relatively large tube, the velocity is the rate of flow divided by the cross section. The loss of velocity of airand abrasive when a tube of considerably larger d1- ameter than the nozzleis affixed t'o the'nozzle for the purpose ofcleaning the inside of the tube is such that the velocity of the abrasive is not suiiicient for effective cleaning so that the 'cleaning operation cannot be accomplished economically in this way. 'Itis also of interest that the attempt to blast or clean such tubes under these circumstances leaves anunblasted length of two inches or more at the inlet end. A urther diiiculty results from the deposit of abrasive within the tube 1931. Serial No. 531,659.

due to the comparatively low velocity of the air and abrasive and the loss of energy of the abrasive caused by impacting of the particles against the walls of the tube. This deposit Jorms'a protective layer which prevents or greatly retards the blasting or Icleaning action.

By means of thepresent invention the previously existing diiiculties in connection with the sand blasting of the inner surfaces of tubes have been overcome and means has been devised whereby a maximum velocity of the air and abrasive flow is obtained irrespective of the size of the tubes or pipes to .be cleaned.

The loss of economy, being due to the necessity under the former practice for supplying sutlicient compressed air to maintain a continuous blast through the relatively large tubes at a velocity suiiicient for sand blasting purposes, the dilculty has been overcome by the inventive conception that the introduction of abrasive and the operation of the blast can be performed intermittently, and preferably alternately giving the desired results in the way of an eicient and complete cleaning of the interior surfaces with a relatively small' consumption of compressed air and abrasive.

To this end in applicants preferred apparatus an explosion or blast chamber is so arranged in connection with a supply of air under pressure and an abrasive tank with a quick operating air valve as a gate valve ory the like in the air passage leading to the leased intermittently at the will of the operator or by automatic control at suitable intervalsso that the air blastis projected* at high velocity through the blast chamber or explosion chamber, and is then 4almost immediately discontinued before f the air presblast chamber` that the air blast can be resure back yof the blast is dropped below a predetermined minimum. The term air is used for convenience as any other fluids may be utilized within the scope of the invention.

Between thefblasts the abrasive is caused to accumulate'in-the blast chamber or eX- plosion chamber, beingpreferably cut olf in any suitable manner either automatically or otherwise Ito preventy back flow through the abrasive supply. rl"he explosion chamber is also -preferably provided at the end opposite to the air valve with'a suitable connection for -engaging the various sizes of tubes .to be treated, the same adapter.- 4 In the performancev of the Amethod of the invention, the tube tobe blasted is connected to the explosion chamber by means of -theadapter or in any suitable manner on the opposite side thereof from the air valve. --The tank, is at the sametime duly supplied with abrasive. The air reservoir or receiver which is located adjacent .the explosion chamberto afford@ supply of air under pressure immediatelyl available, without too great a pres.

sure drop, for the purposes of blasting, is connected to the air mainl or any suitable supply of air under pressureor a suicient supply of air or other fluid capable of being utilized in'thisway is connected to the eX- plosion chamberby way of the quick operat-l ing valve. The quick operating valve adjacent theexplosion chamber is .then opened for a momentand closed almost immediately or when the pressure gauge showsV a certain vpredetermined drop. The valve is then -caused or- Apermitted to remain closed until the pressure in the air tank or receiver is built up to normal and the abrasive flow, which was cut off duringr the air blast, is supplied to the chamber. yThe air valve is then 4 reopened and the process is continued passing a series of short quick jets or blasts of air and abrasive through the tube until the blasting or cleaning of the tube has been accomplished to the desired degree of perfecf tion.

-lustrated a sand blasting aparatus of the explosion or intermittent type, the same being an embodiment of my invention insofar as it t rtrolled for this of 'the invention, the apparatus being conor byhand.

In the drawings: i Figure 1 is an elevation ofthe apparatus in the operation of. cleaning the inside of a tube 1n accord-ance with the method of the invention including an automatic device for operating the air valve. f

Figure 2 is an elevation ofthe apparatus on an enlarged scale, aportion'of the explosion'chamber being broken away to show the being referred to as an' Every time the air valve is opened, theretakes place a sudden rushof air through the purpose either automatically.

'inside of the chamber. Theapparatus in ac# view is adapted to handn cordance with this operation. l v

Figure 3 is an elevation of the air valve and the solenoids for operating the same, taken on the line 3-3 in Figure 1 and looking to the left.

lFigurel is a circuit diagram showing the air valve in external elevation, the view of the valve being taken from the line 3-'3 in Figf ure l.

lReferring to the drawings by numerals, each of which is used to indicate the same or similar parts in the different figures, the apparatus, Figure 1, comprises an air receiver 1,

connected at 2 to an air main or supply of air under pressure, a storage tank 3 for abrasive and explosion chamber 4 connected to the bottom of the storage tank by an upright passage 5 in which is mounted a check valve 6. On lone side of the 'explosion chamber is the quick operating air valve 7 controlling an air passage 8 leading from the receiver 1 to the explosion chamber 4 and on the other side of the explosion chamber which is shown in the form of a tubula` member, is the 'work connection or tube adapter 9. The abrasive pas'- sage 5 enters the explosion or blast chamber 4 laterally and preferably from thetop side as' shown. The apparatus also includes an air pressure gauge 11 'shown as mounted on the air receiver 1, and suitably connected thereto to indicate the pressure therein. This air gauge may also be utilized as an element of the automatic operating means serving to make vand break the electric circuit in the operation fof the air valve in response to changes of pressure-as hereinafter described.

A similar apparatus is shown fragmentarily in Figure 2 infront elevation which corresponds `to Figure 1.

In 'the illustration, Figure 2, the ai-(valve 7 which is shown in detail in dotted lines, is con-v trolled and operated by a hand lever 10. In Figures 1, 3 and 4, onthe other hand, I have illustrated more or less diagrammatically an automatic .device for operating the air valve 7 periodically in response to the changes of pressure in the receiver and substantially in accordance with the requirements for pro- .ducing the desired result most efficiently. relatesto the'apparatusand beingl capable of operation-in the performance 4of the method Referring more particularly yto-the details of the apparatus, the airfvalve 7 is shown as comprising "a gate valve member 14 mounted to slide vertiallyand transversely tothe air Apassagef8,,infjways11i-'5"forrnetl*of this purl pose-in the valve' fitting I6: 1 'IIii's 4gatevalve member is shown 'as-provided-,witli' a trans-- verse.stud or pin 17 seated iny an upwardly projecting lug 18 on the 'upper sidetof .the valve member near the center. This pin is engaged by slot 19 in the transverse arm 20 of a bell crank leverpivoted at 21 in the valve fitting or casing andhavingan upper arm 22 substantially at right angles to'lthe arm 20.

This arm 22 is connected at its upper end by means of a pin 24 and slot 25 to a sliding shaft 26 carried by the cores 27 and 28 of two solenoids 29, 30, arranged in alignment transverse to the air passage 8 and substantially over the valve fitting or casing 16. 51 is a spring cushioning device to break the shock to t e apparatus incident to the quick operation of the solenoids.

For the purposes of the automatic operation of the air valve 7, thepointer or hand 32 of the air pressure gauge 11 is shown as' connected to one terminal of an electric battery 33 in any suitable nner as by way of a control switch 34. j he gauge 1s also provided with electric contacts 35, 36 in the path of the hand or indicator 32 to be engaged thereby at certain predetermined maximum and minimum pressures. These terminals or contacts 35, 36 may, if desired, be supported for adjustment in a circular arcuate slot 37 whereby the maximum and minimum points of contact may be determined in accordance with the will of the operator, or they may be permanently located as desired.

These Contact points or terminals 35, 36

are connected to magnetic switches 55, 56,'

respectively, each of which` controls a corresponding solenoid 29, 30. VThese solenoids are in turn connected to an outside source of current at 58.

In this way either solenoid may be separately energized by closing either contact at the gauge. Contact 35 is closed at minimum ressure and 36 at maximum pressure. Vhen contact 35 is engaged by the pointer 32, the switchA 35 is closed and energizes the solenoid 29, closing the valve 7. When con-` tact 36 is engaged by the pointer, the switch 56 is closed energizing thesolenoid .30 and openinor the valve 7.

The illustrationkFigures 1 and2, includes check valve 6 in the vertical passage 5 leading downwardly from the abrasive storage tank 3 to the ex losion chamber` 4. This check valve which under certain circumstances might not be regarded as necessary to the successful operation of the apparatus, is shown in the form of a ball valve opening downwardly and supported in its lower position by a stop 42. y

Figure 2 shows the explosion chamber 4 which is preferably tubular or cylindrical as rifled, to give a swirling or rotary motion of the air causing the abrasive to1 be thrown radially outwards due to centrifugal force with the' result vthat it comes into contact with the inner walls of the tube to be cleaned. This riling may, however, be omitted and the details of the apparatus may be widely varied without departure from the principle of the invention. The riiing is believed to give better results.

In the operation, as already suggested in the preamble, atube isl suitably held in alignment with the explosion chamber 4,"

tank or reservoir 3 is supplied with abrasive and air is admitted to the receiver 1. Under these circumstances the weight of the abrasive 46 opens the valve 4() and the abrasive iows downwardly into the explosion chamber 4 into the line of the air blast. The abrasive thus admitted accumulates at 47 in the explosion chamber and in the path of the air blast as outlined in Figure 1.

The receiver 1 being suitably supplied with air under pressure as already suggested, the air valve 7 may be opened intermittently at the will of the operator and closed immediately or when the pressure gauge shows a certain predetermined pressure drop. The valve 7 is then caused to remain closed until the pressure in the receiver 1 is again built up to line pressure by the admission of air from the line. The valve is then again opened and the operation repeated five to ten times or until the inside of the tube being treatedis sufficiently cleaned or blasted.

When the valve 7 is thus suddenly opened, a rush of air through the explosion chamber takes place carrying with it the accumulated abrasive 47 which is thus expelled with great force at the end of the tube 45 being treated. Experiments with this method and apparatus show that smooth steel tubing requires about ve to ten shots in this jmanner.

If the apparatus is to be operated automatically, the switch 34 is .closed'and the pressure being registered by the swinging of the indicator 32 to the right or clockwise in Figure 3, the attainment of any predeterminedor line pressure will bring this hand or indicating pointer 32 in contact with the' terminal or contact member 36. Under these circumstances the solenoid 30 will be energized, drawing the core 28 to the right in Figures 3 and 4, raising the gate valve member 14 and opening the valve 7 to permit 'a rush of air from the receiver 1 through the explosion chamber 4 as already described, carrying the abrasive with high velocity from the chamber and through the tube 45, eliminating any possibility of accumulation of abrasive therein. The abrasive may be caughtin a suitable abrasive receiving and separating chamber, indicated at 50.-

When the pressure in the receiver 1 has dropped to a predetermined point, the hand 1 or indicating pointer at 32 swings to the left in Figure 4 and comes in contact with-the terminal 35, energizing the left hand solenoid 29 and closing the valve 7 whereupon this valve remains in closed position until the pressure in the receiver 1 is built u to the predetermined line pressure when t e valve i of the inside of the tube or other` hollow work flo.

has been completed to the desired extent.

WhileI have' referred to compressed air as the most convenient medium. for propelling sure, may be used. Compressible Hui the abrasive, it will be understood that other fluids, as steam and even water,'underdpres' s, as gases or liquids propelled by air or similar resilient pressure, are most conveniently available for'this purpose. The term air, as

used in the specificationand claims, is intended to include any iuid element adaptedl to propel abrasive.

I have thus described specifically and in detail the method 'of sand blasting tubes and other vhollow shapes according to the invention and an apparatus by means of which this method may be performed,`which apparatus is also a .feature 4of the invention, the description being specific and in detail in order that the invention and the manner of operation, applying and using-the same may be fully understood, however the specific terms herein are used descriptively rather than in a limiting sense, the scope of the invention being defined in the claims. What I claim as new and desire to' by Letters Patent is:

1. An apparatus for blasting the inside of long tubular objects with abrasive coinprising an air receiver of suitable proportions, a quick acting control valve, an explosion chamber connected to the receiver Secure through the control valve', means for for preventing backflow through the abrasive supply and means for connecting a tubular object to the explosion chamber.

2. The method of sand blasting particularly adapted to the' treatment of the inner surfacesof tubular objects and the like which consists of projecting abrasive through the tubular work against the said surfaces by means of intermittent blasts' of *air under pressure.

3. The method of sand blasting particuy lai-ly ladapted to the treatment of the inner surfaces of tubular objects and the like which consists of projecting abrasive into, to and through said tubular work land against the said surfaces by means of intermittent blasts of fluid Aunder pressure, the abrasive being introduced into the path of the iuid between .the blasts, whereby a relatively large flow of charges of abrasive `through the said tubular 'a supply of air under pressure, means confaces of tubular and similar work which con- 7 `sists in releasing at predetermined intervals successive blasts ofair under pressure and introducing into. the air blast successive work, projecting the abrasive and directing said intermittent blasts of air and'abrasive against a surface to Abe treated and imparting a swirling motion to the air and to the abrasive whereby a centrifugal tendency is imparted to the abrasive, projecting it against said surface.

. 5. A sand blasting apparatus comprising an explosion chamber, `means for introducing V blasts of airinto the chamber at intervals, means for introducing successive charges of i abrasive into the path of the air between the blasts and means for directing the sucx cessive blasts of air and abrasive into contact j with the work and means for imparting a swirling motion to the air. i

6. In a sand blasting apparatus an explosion chamber, al receiver for air under pressure, means for connecting the receiver to necting the receiver to the explosion chamber, a quick acting valve Abetween the mixer and the receiver, means for introducing abrasive into the path of the air in the explosion cham ber, and means for operating the airvalve at intervals to produce a succession of air blasts through the mixing chamber.

7. In a sand blasting apparatusan explosion chamber, a receiver -for fluid under pressure, means for connecting the receiver toa supply ofy fluid under pressure, means connecting the receiver to the-explosion chamber, a quick acting valve between the chamber and the receiver, means for accumulatingsuccessivechargesof abrasive in the path of the '110 iiuid in the explosion chamber, and means, for operating the iuid valve to produce a succession of air blasts through the explosion chamber, said means being controllable in accordance with the rise and fall of pressure in the receiver.

8. In a sand blasting apparatus an explosion chamber, a receiver for air under pressure, means for connecting the receiver to a supply of air under pressure, ineans connecting the receiver to the explosion chamber, a quick acting valve between' the mixer and the receiver, means for introducing abrasive@ into the path of the air in the explosion cham- I ber, a check valve for preventing backflow,

' and means for operating the air valve at intervals to produce a succession of air blasts through the mixing'chamber, said means being controlled in accordance with the rise and fall of'pressure lin the receiver, to conino t trol the pressure in the receiver, causing it to be lowered to a predetermined minimum pressure after each opening of the valve before it is closed, and permittmg the pressure to be raised ater closing to the predetermined maximum prior to each operation of the valve in opening.

9. The combination in a sand blasting aparatus of an explosion chamber, means for introducing airunder pressure at one end and means for directing the blast against the Work at the other end, means for mtroducing successive charges of abrasive into the chamber, including ai abrasive supply passage anda check val controlling t e same an air valve controlling` the introduction of air, va receiver for air and means for controllingrthe air valve to open it at a predetermined maximum pressure in the receiving chamber and close it at a predetermined minimum pressure in the receiver, the openiig and closing being accomplished contmua y to produce a succession of air blasts inl and through the explosion chamber, alternatinv with. the feeding'of abrasive thereto.

ignedby me at Hagerstown, Maryland,

this 14th day of April, 1931.

WILLIAM A. ROSEIIBERGHER.4 

